Index: Lib/csv.py
===================================================================
--- Lib/csv.py	(revision 65223)
+++ Lib/csv.py	(working copy)
@@ -77,15 +77,15 @@
         self.reader = reader(f, dialect, *args, **kwds)
         self.dialect = dialect
         self.line_num = 0
+        if self.fieldnames is None:
+            # First row of the file is taken to be the column headers.
+            self.fieldnames = self.reader.next()
 
     def __iter__(self):
         return self
 
     def next(self):
         row = self.reader.next()
-        if self.fieldnames is None:
-            self.fieldnames = row
-            row = self.reader.next()
         self.line_num = self.reader.line_num
 
         # unlike the basic reader, we prefer not to return blanks,
Index: Lib/test/test_csv.py
===================================================================
--- Lib/test/test_csv.py	(revision 65223)
+++ Lib/test/test_csv.py	(working copy)
@@ -611,6 +611,7 @@
             fileobj.write("f1,f2,f3\r\n1,2,abc\r\n")
             fileobj.seek(0)
             reader = csv.DictReader(fileobj)
+            self.assertEqual(reader.fieldnames, ["f1", "f2", "f3"])
             self.assertEqual(reader.next(), {"f1": '1', "f2": '2', "f3": 'abc'})
         finally:
             fileobj.close()